Water mass transformations and air-sea exchange in the Barents Sea

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Abstract

Water mass transformation processes in the Barents Sea and their interannual to decadal
variability are studied using a regional coupled ice-ocean model and observational data.
Long-term data allows for assessment of temporal and spatial variability in water mass
properties and distribution, and the influence on air-sea exchange of heat and CO2.
The Barents Sea ocean climate shows substantial interannual to decadal variability
between 1948 and 2007. Variations in ocean heat transport associated with the Atlantic
inflow modulate both the Barents Sea mean temperature (heat content) and the sea-ice
extent. An increasing ocean heat transport is largely responsible for the sea-ice retreat
in the Barents Sea during recent decades. The increased open ocean area causes a larger
heat loss to the atmosphere, which provides sufficient cooling to transform a majority of
the warm Atlantic inflow into cold, dense water before it is exported into the deep Arctic
Ocean. The Barents Sea is thus an effective ocean cooler, and the dense outflow into the
Arctic Ocean displays large variability, corresponding to variations in the Atlantic inflow.
Variability of water mass transformation processes related to changes in surface heat
loss, sea-ice growth and corresponding salt fluxes, and the surface salinity before winter,
also leads to substantial variations in the thermohaline properties of dense water. In the
southern Barents Sea this is associated with the Atlantic inflow and thus the regional
climate, whereas variable preconditioning of surface waters by ice melt and fresh coastal
waters are more important in the northern Barents Sea.
Oceanic heat loss and convective processes also favor an uptake of atmospheric CO2.
Calculated air-sea CO2 fluxes for the period 2000-2007 identifies the southern Barents
Sea as a particularly efficient sink of atmospheric CO2. Temporal and spatial variability
of water mass properties and sea-ice extent are important to the CO2 uptake, although
wind speed is the major driver of variability.